The present invention relates to laser technology. More particularly it relates to a method for laser micromachining with a plurality of beams and apparatus thereof.
Laser techniques and laser devices have developed remarkably since the invention of the laser (see early patentsxe2x80x94the ruby laser device, U.S. Pat. No. 3,353,115, to Maiman, and U.S. Pat. No. 4,053,845 and 4,704,583 to Gould, relating to optically pumped laser amplifiers).
Laser radiation is widely used in a large variety of applications, material processing being a major field of laser use. There are well-known techniques of cutting, welding, drilling of non-transparent materials. A very important field of laser application is the three dimensional structuring of transparent dielectrics, based on the intravolume optical breakdown phenomenon, especially with ultra fast laser radiation.
In U.S. Pat. No. 4,950,862 (Kajikawa), filed in 1989, titled LASER MATCHING APPARATUS USING FOCUSING LENS-ARRAY, there was disclosed a laser beam matching apparatus for finely matching a semiconductor circuit or similar workpiece on a stage. It includes a scanning mirror for directing the beam, scanning lens for converting the beam to a beam substantially perpendicular to the workpiece, lens array unit and mask for focusing the beam, driving means for X-Y movement of the lens array unit and control means for controlling the mirror driving means and stage.
In U.S. Pat. No. 5,517,000 (Nishiwaki et al.), filed in 1994, titled APPARATUS FOR FORMING A WORKPIECE USING PLURAL LIGHT BEAMS, there was disclosed a plurality of elongated beams generated by dividing a laser beam, said plurality of beams being respectively applied to corresponding lens elements of a flyeye lens array. The structure is arranged in such a manner that the diameter of the plurality of the beams in the shorter dimension is made smaller than that of each of the lens elements, so that the plurality of beams is further divided into a plurality of elongated secondary beams by the flyeye lens. The plurality of secondary beams is bundled in a diaphragm in such a manner that their lengthwise directions substantially coincide with each other so that a beam pattern is formed. A row of openings arranged in the lengthwise direction of the beams pattern and formed in the diaphragm member are uniformly and efficiently irradiated with the thus-formed beam pattern. Then, the image of the row of openings is projected onto a plastic plate or the like, so that a multiplicity of holes is formed in the plate. As a result, a nozzle plate of an ink jet printer head can be accurately and quickly manufactured.
In U.S. Pat. No. 5,521,628 (Montgomery), filed in 1993, titled LASER SYSTEM FOR SIMULTANEOUSLY MARKING MULTIPLE PARTS, there was disclosed laser marking systems having increased part throughput, which are obtained by disposing diffractive optics across a primary laser beam. Preferred diffractive optics for high power marking lasers are defined in optical materials with discrete surface levels. This system provides identical and simultaneous marking.
In U.S. Pat. No. 5,656,866 (in den Baumen et al.), filed in 1995, titled APPARATUS FOR LASER MATCHING WITH A PLURALITY OF BEAMS, there was disclosed an apparatus for laser matching by creating a plurality of discrete and separate beams which are sent to a deflecting device including a support and a plurality of individual deflecting elements that act independently and are individually controlled to machine different points on the workpiece simultaneously. It is noted that in the apparatus disclosed in this patent the control of each deflecting element is mechanical, and therefore it is suggested that the response time for each deflecting elements to reorientation command may substantially limit the overall performance of the apparatus.
U.S. Pat. No. 6,037,564 (Tatah), filed in 1998, titled METHOD FOR SCANNING A BEAM AND AN APPARATUS THEREFOR, disclosed a method for directing a light beam to a substrate and an apparatus to do the same. A single light beam is directed to a diffractive element. The diffractive element diffracts the single light beam to form a plurality of light beams. A controller generates a first control signal for controlling a digital micromirror device, which selectively directs each of the plurality of light beams toward or away from the substrate. A lens focuses each selectively directed beam onto the substrate.
A main object of the present invention is to increase the productivity of laser-based technologies and improve the quality of laser treatment.
A main aspect of the present invention is to divide a primary laser beam into a plurality of laser beams, each modulated separately and independently, thus achieving multi-tasking performance where each modulated beam carries out a predetermined part of the overall task, and where the plurality of beams perform together the entire task.
Another aspect of the present invention is to modulate the intensity of each one of the beams independently using a light modulator array, as opposed to mechanically controlling each beam, thus gaining faster response times, and hence faster performance.
Yet another aspect of the present invention is to focus each beam on or below the surface of the workpiece by a single element of microlens array. In accordance with the present invention the productivity increase depends on the number of focusing elements and on the primary laser beam intensity. The quality of processing is improved due to the modulation of the laser beam intensity and consequently damage spot size control.
It is therefore thus provided, in accordance with a preferred embodiment of the present invention, an apparatus for laser machining for optically machining a workpiece, the apparatus comprising:
a plane polarized primary laser beam source adapted to generate a primary plane polarized light beam;
a beam splitter, adapted to split the primary light beam into a plurality of secondary light beams;
a light modulator array, comprising an array of individually controllable elements that are each adapted to be set to either allow each beam of the plurality of secondary light beams to traverse through, or effectively block it;
a microlens array, comprising an array of microlens elements foci of predetermined lengths, said microlens array elements corresponding to the elements of the light modulator array so that light beam passing through an element of the light modulator array is focused by a corresponding element of the microlens array; and
control means adapted to independently switch each of the elements of the light modulator between a transparent and opaque modes in a predetermined manner.
Furthermore, in accordance with another preferred embodiment of the present invention, the apparatus further comprises support means for supporting the workpiece during operation.
Furthermore, in accordance with another preferred embodiment of the present invention, the apparatus further comprises repositioning means for repositioning the workpiece, and wherein said control means is also adapted to operate the repositioning means so as to reposition the workpiece between desired positions.
Furthermore, in accordance with another preferred embodiment of the present invention, said repositioning means comprise motor-driven moving stage.
Furthermore, in accordance with another preferred embodiment of the present invention, said motor-driven moving stage is computer-controlled.
Furthermore, in accordance with another preferred embodiment of the present invention, the intensity of the light beams focused by the apparatus on the workpiece is sufficient to cause optical breakdown in the workpiece.
Furthermore, in accordance with another preferred embodiment of the present invention, said laser beam source is a continuous wave laser.
Furthermore, in accordance with another preferred embodiment of the present invention, said laser beam source is a pulsed laser.
Furthermore, in accordance with another preferred embodiment of the present invention, the pulse duration is in the order of 10xe2x88x929 seconds or shorter.
Furthermore, in accordance with another preferred embodiment of the present invention, the light modulator array is a LC-based array.
Furthermore, in accordance with another preferred embodiment of the present invention, said LC-based array is computer-controlled.
Furthermore, in accordance with another preferred embodiment of the present invention, the apparatus further comprises beam steering scanner positioned between said light modulator array and microlens array, so as to steer the secondary light beams thus increase the work span of the apparatus.
Furthermore, in accordance with another preferred embodiment of the present invention, said beam steering scanner is a galvanometer scanner.
Furthermore, in accordance with another preferred embodiment of the present invention, said beam steering scanner is a piezo-optical scanner.
Furthermore, in accordance with another preferred embodiment of the present invention, said beam steering scanner is an acousto-optical scanner.
Furthermore, in accordance with another preferred embodiment of the present invention, the microlens array comprises an array of refractive lenses.
Furthermore, in accordance with another preferred embodiment of the present invention, the microlens array comprises an array of diffractive lenses.
Furthermore, in accordance with another preferred embodiment of the present invention, the apparatus is further provided with user interface for inputting user commands to the control means.
Furthermore, in accordance with another preferred embodiment of the present invention, said user interface comprise a keyboard.
Furthermore, in accordance with another preferred embodiment of the present invention, said user interface comprise a touch screen.
Furthermore, in accordance with another preferred embodiment of the present invention, there is provided an apparatus for laser machining for optically machining a workpiece, the apparatus comprising:
a plane polarized laser beam source adapted to generate a primary plane polarized light beam of predetermined polarization;
a beam expander, adapted to expand the primary light beam laterally;
a light modulator array, comprising an array of individually controllable elements that are each adapted to be set to either allow portion of the primary light beam to traverse through, or effectively block them;
a microlens array, comprising an array of microlens elements with foci of predetermined lengths, said microlens array elements corresponding to the elements of the light modulator array so that light beam passing through an element of the light modulator array is focused by a corresponding element of the microlens array; and
control means adapted to independently switch each of the elements of the light modulator between transparent and opaque modes in a predetermined manner.
Furthermore, in accordance with another preferred embodiment of the present invention, there is provided a method for laser machining of a workpiece, comprising:
providing a laser beam source;
providing a light modulator array, comprising an array of individually controllable elements that are each adapted to be set to either allow a single beam of plurality of light beams to traverse through, or effectively block it;
providing focusing means for the light beams emerging from the light modulator array;
splitting said laser beam to a plurality of secondary light beams;
irradiating the plurality of secondary light beams onto said light modulator array, and switching each of the elements of the light modulator array between transparent and opaque modes in a predetermined manner; and
focusing light beams emerging from said light modulator array on the workpiece.
Furthermore, in accordance with another preferred embodiment of the present invention, the method further comprises repositioning the workpiece in a predetermined manner, so as to increase the processed zone of the workpiece.
Furthermore, in accordance with another preferred embodiment of the present invention, the light beams emerging from said light modulator array are focused on a surface of the workpiece.
Furthermore, in accordance with another preferred embodiment of the present invention, the light beams emerging from said light modulator array are focused within the workpiece.
Furthermore, in accordance with another preferred embodiment of the present invention, the method further comprises further causing optical breakdown by the light beams emerging from said light modulator array.
Furthermore, in accordance with another preferred embodiment of the present invention, the laser beam source is a continuous wave laser.
Furthermore, in accordance with another preferred embodiment of the present invention, said laser beam source is a pulsed laser.
Furthermore, in accordance with another preferred embodiment of the present invention, the method further comprises providing angular steering of the plurality of secondary light beams, so as to increase the work span of these beams.